BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. PEEL : PULP : Green bananas ... Ripe ? ? ... Green bananaR ... Ripe 9 9 ... 241 41-72 36-51 5-21 0.55 0.34 0.26 0.37 0.29 ' 0.10 2.02 3.75 1 038 36'38 31.50 4.88 0'56 0'38 0.23 0.39 1'35 0.04 0'71 2-27 I 0.32 58.28 41'35 16'93 0'51 0'29 0.70 0'14 0'37 0'48 13'15 1;:;: i 0.40 59-73 42.99 16'74 0'51 0.28 0.74 0'14 10'34 1'52 2'40 0'18 BACTERIOLOGICAL, PHYSIOLOGICAL, ETC.Changes in Composition of Ripening Bananas. H. C. Gore. (J. Agric. Besewch, 1914, 3, 187-203.)-West Indian bananas were used for the experiments, two of which were conducted by placing bunches of green bananas to ripen in a large respiration calorimeter designed for experiments with man, while in the other two R specially designed ripening chamber was employed in order to investigate the rate of starch hydrolysis during ripening in relation to changes in the rate of respiration.The following figures were obtained, showing the composition of bananas before and after ripening in the respiration calorimeter : COMPOSITION EXPRESSED IN TERMS OF PERCENTAGE OF PEEL OR PULP WHEN ANALYSED. PULP : Ripe 9 9 ... 1 62-15 , 71-98 28'02 0.85 0'47 1-24 0'24 17-31 2.54 4.84 1'94 1 ff 1 :::: 22'66 26'28 0.69 4'02 0-30 COMPOSITIOlS EXPRESSED IX TERMS O F THE WHOLE GREEN BANANAS.*242 ABSTRACTS OF CHEMICAL PAPERS The principal change during ripening is the conversion of starch into sugars, which proceeds most rapidly while the fruits are turning from green to yellow.During this period the respiration-rate increases manyfold, becoming greatest at the time when tho rate of starch hydrolysis is most rapid.Starch hydrolysis then gradually slackens, later ceasing altogether. The respiration-rate, too, becomes slower, but still remains far more active than in the green fruit. The peel loses, while the pulp gains weter'steadily; the increase in water in the pulp during ripening being all derived from the peel except when bananas become over-ripe, when the water formed in respiration may more than balance the water absorbed in starch hydrolysis.The quantities of ash, protein, and ether extract undergo but slight changes during ripening, while pentosans decrease markedly in the pulp but remain little changed in the peel. Carbohydrates were determined by extracting weighed samples with 80 per cent.alcohol, the residues being dried and weighed and the weighed portions used in the estimation of starch and pentosans. The extracts were evaporated nearly to dryness with a little calcium carbonate, and after treatment with lead acetate were used for the estimation of reducing sugar and cane sugar. Starch was determined in the alcohol-insoluble portion by hydrolysis with hydrochloric acid.H. F. E. H. Ability of B. cold to survive Pasteurisation. S. H. Ayers and W. T. Johnson, (J. Agric. Research, 1915, 3, 401-409.)-The thermal death-point of 174 cultures of B. coli isolated from cow faxes, milk and cream, human faeces, flies and cheese, showed considerable variation when the cultures were heated in milk for thirty minutes under conditions similar to pasteurisation.At 60' C., the lowest pasteurising temperature employed, 95 cultures, or 54.6 per cent., survived ; at 62.8' C., the usual pasteurising temperature, 12 cultures, or 6.9 per cent., survived. One culture was not entirely destroyed at 65.6' C., but in repeated experiments this temperature always proved fatal. There is a, marked difference in the effect of heating at 60" C.and 62.8' C. Although the difference in temperature is only 2.8" C., yet it was found that 87 per cent. of the cultures that survived at 60' C. were destroyed at 62.8' C. Considerable variation was found in the thermal death-point of the colon bacilli which survived at 62.8" C. When the 12 cultures that survived were heated again at the same temperature, it was found that many did not survive, and in each repeated heating different results were obtained.It would appear that 62.8" C. maintained for thirty minutes is a critical temperature for colon bacilli. Among the 174 cultures examined, all were found to have a low majority thermal death-point, but were able to survive pasteurising temperatures in virtue of the survival of a few cells. An attempt to make the colon bacillus test an index of the efficiency of the pasteurisation process is thus complicated by the ability of certain strains to survive a temperature of 62.8' C.for thirty minutes and to develop rapidly when the milk is then held under temperature conditions which might be met with during storage and delivery, Experiments so far made indicate that no cdon bacilli will survive thirty minutes heating to 65.6' C., though such heat-resisting strains may yet be encountered.H. F. E. H.BACTERIOLOGICAL, PHYSIOLOGICAL, ETC. 243 Studies on Enzyme Action. XIII. : The Lipase of Soya Beans. K. G. Falk. (J. Amer. Chem. SOC., 1915,37,649-653.)-The lypolytic properties of soya beans were studied by the methods used in the similar studies of castor beans and of duodenal contents.Soya beans contain a lipase active towards triacetin (and therefore pre- sumably towards fats), somewhat soluble in water, with a maximum solubility in 1.5 N-sodium chloride solution. Castor beans contain an esterase soluble in water, and a lipase insoluble in water and soluble in sodium chloride solution, with maximum solubility at a concentration of 1.5 N.Duodenal contents contain an esterase and a lipase, the former predominating in the intestinal juice and the latter in the pancreatic juice and bile. Marked similarities in the action of neutral salts and alcohols are shown by the lipases from different sources. The action of heat and of drying on the soya bean lipase was found to be similar to their action on castor bean lipase and esterase.The analyses of the soya bean lipase preparations showed no marked differences in comparison with the analyses of the castor bean preparations. J. F. B. Mouldiness in Butter. C. Thorn. (J. Agric. Research, 1915, 3, 301-309.)- The following three forms of mould are most usually met with in butter : (1) Orange- yellow areas with a submerged growth of mycelium produced by Oidium lactis.(2) Smudged or dirty-green areas either entirely submerged or with some surface growth produced by species of Alternuria and Cladosporium. (3) Green surface colonies produced by species of PemkiZlium, or more rarely Aspergillus, either upon the butter, causing decomposition, or upon the container or wrappings, injuring the appearance of the sample in the markst.The occurrence of any of these forms in a sample of butter indicates low salting, since species of Oidium alternaria and CZadosporium cannot develop in butter containing 2.5 per cent. of salt. Excess of curd is found to favour mould growth, while well-washed butter is less subject to mould. Leaky butter-butter from which water of buttermilk exudes and collects in the wrappings or in the container-furnishes the best conditions for the beginning of mould growth, while from these'wet area8 colonies may spread to the butter itself.Mould will not grow upon the surface of a piece of butter exposed to humidities of 70 per cent. or lower. The water in the butter is thus not suficiently available to the mould to support the development of the colony unless evaporation be reduced by high humidities; Wet surfaces and wet wrappings must therefore be strictly avoided, A salt content of from 2.5 to 3 per cent.in butter is sufficient to eliminate mould or reduce it to a negligible amount, This is equivalent to the use of a 12 to 15 per cent. brine. H. F. E. H. Estimation of Sulphur in the Culture Medium for the Detection of the Bacteria producing Hydrogen Sulphide.H. W. Redfield and C. Huekle. (J. Amer. Chem. SOC., 1915, 37, 612-623.bThe methods standarised in the paper (see p. 250) were applied for the study of the changes brought about by the activity of sewage bacteria in culture media composed of peptone and potassium chloride. The following facts were established : The portion of the peptone medium which is insoluble in water contains the same percentage of sulphur as the soluble244 ABSTRACTS OF CHEMICAL PAPEES peptone ; filtration of the medium is therefore not essential.In cultures inoculated with artificial sewage and incubated at 38O C. for forty-eight hours, the ratio of total solids (excluding potassium chloride) to total sulphur is very nearly the same in the soluble and insoluble portions; hence the insoluble matter may be regarded as consisting mainly of peptone.The production of hydrogen sulphide by the bacteria present in the sewage employed was 50 per cent. greater when a current of air was passed over the surface of the culture than in the quiescent state, and 100 per cent. more than when a current of carbon dioxide was passed through the flask.In tt current of air 25 to 30 per cent. of the total sulphur was converted into hydrogen sulphide in forty-eight hours; 50 to 60 per cent. in seventy-two hours. For the estimation of the hydrogen sulphide evolved, the volumetric iodine method is inaccurate, probably because of the presence of unsaturated volatile organic com- pounds. The best method consists in absorbing the volatile sulphides in potassium hydroxide and determining the sulphur by the Liebig-Koch method.In order to expel all the volatile sulphides at the end of the period of observation, the cultures were heated on the water-bath for thirty minutes while a current of air was passed through. The sulphur retained in the cultures as non-volatile sulphides was determined by adding 25 C.C. of concentrated hydrochloric acid to 300 C.C. of the culture and distilling under reduced pressure for thirty minutes into a wash-bottle containing sodium peroxide solution, then estimating the sulphur by the Liebig-Koch method. The total sulphur-easily oxidisable sulphur and loosely bound sulphur- remaining unattacked in the culture media were then estimated by the methods already eatablished (see p. 250). Somewhat higher proportions of the loosely bound and the easily oxidisable sulphur were converted by the bacteria into hydrogen sulphide than of the total sulphur. J. F. B.